Drilling a well for tapping underground reservoirs of oil or gas is an expensive procedure that has made the petroleum exploration industry a competitive one where cost improving advancements are continually sought. Oil and gas drilling is currently most commonly accomplished with rotary rigs using conventional joined pipe sections. These rigs typically have jackknife type masts that are tall enough to handle up to 3 stands of joined pipe and thereby facilitate faster "trips" in and out of a well bore. Automatic pipe handling apparatuses have been proposed for simplifying this laborious and time-consuming task (as in U.S. Pat. No. 4,951,759 to Richardson for example), yet drilling procedures today remain very much the same for the past few decades.
Once drilling is finished and the casing has been cemented in the wellbore, the drilling rig is usually moved, and a smaller, truck-mounted service rig is brought in to complete the well. Completing a successful well, namely preparing it for production, typically includes the steps of running a casing into the well, installing a wellhead, and installing a production tubing string. Production tubing strings today may consist of continuous coiled tubing (referred to herein as "CT") carried on a spool on a service rig and which is injected inside the well casing using an injector head to straighten and push the tube down.
Mobile service rigs with a mast for handling conventional pipe sections have been proposed, yet most require separate transport for their masts and all are of limited application. For example, Elliston (U.S. Pat. No. 4,290,495) and Eddy et al. (U.S. Pat. No. 4,036,508) both describe a mobile rig incorporating a mast for effectively handling pipe strings in and out of a well. Neither Elliston nor Eddy offers a service rig adapted to handle other types of drilling or well servicing technology. Mobile rigs for doing continuous tubing drilling (CTD) also exist but most of the CT rigs in use today require the use of a separate crane to manipulate the blow-out-preventer (BOP) and injectors that are needed with this technology. Although there are rigs which have a collapsible mast along which an injector head can be raised or lowered without the need for a crane, such as in Baugh (U.S. Pat. No. 4,265,304), these rigs suffer from various shortcomings. For instance, Baugh is not adapted for servicing slant wells or accepting conventional joined pipe, nor can it perform other tasks such as wireline work. Such rigs also require time consuming removal of the injector head and/or the BOP off the mast for transporting the rig.
Current mobile drilling and service rigs suffer from the further disadvantages. They encounter difficulties in properly aligning the guide path of the mast's traveling block with the centerline of a well. Misalignments often result in undesireable forces and damage to the pipe being run into and out of the well. They also require laborious procedures when assembling a lubricator onto a wellhead. Further, CT service rigs have cartridge assemblies which are reel specific in that they can only handle a CT reel designed for that particular cartridge. Hence, CT must invariably be re-spooled from a shipping reel to the cartridge's work reel, wasting time and money. A CT unit operator typically needs to purchase an additional work reel for this purpose, which reel may cost up to US$100,000.
What is desired therefore is a novel multi-task rig which overcomes the many disadvantages of the prior art devices. The novel rig should be mobile and combine on a single platform the ability to transport and operate equipment for continuous coiled tubing drilling, conventional pipe drilling and wireline operations. In particular, the rig should have a pivotal derrick for vertical and slant well operations, and an ability to tilt more than 90 degrees. A CT injector should remain in the derrick at all times without removal for rig transport. The CT injector should be movable out of the plane of the derrick to free the derrick for running conventional joined pipe. The rig platform should be hydraulically movable to help align the derrick with the well, and the derrick's injector should further be maneuverable in 3 dimensions for alignment with the well. A cartridge assembly carried by the rig should be adjustable for receiving various sizes of CT reel. A wireline winch assembly should also be mountable on the platform and be wired to a control cabin for controlling the wireline equipment as well as most other rig systems from a single location.